Files.app: Show thumbnail of non-image file even when the file cache is present

ui/file_manager/video_player/js/video_player.js

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 'use strict';
 
 /**
  * @param {Element} playerContainer Main container.
  * @param {Element} videoContainer Container for the video element.
  * @param {Element} controlsContainer Container for video controls.
@@ skipping 297 matching lines @@
     this.controls.casting = !!this.currentCast_;
 
     videoPlayerElement.setAttribute('loading', true);
 
     var media = new MediaManager(video.entry);
 
     Promise.all([media.getThumbnail(), media.getToken()])
         .then(function(results) {
           var url = results[0];
           var token = results[1];
-          document.querySelector('#thumbnail').style.backgroundImage =
-              'url(' + url + '&access_token=' + token + ')';
+          if (url && token) {
+            document.querySelector('#thumbnail').style.backgroundImage =
+                'url(' + url + '&access_token=' + token + ')';
+          } else {
+            document.querySelector('#thumbnail').style.backgroundImage = '';
+          }
         })
         .catch(function() {
           // Shows no image on error.
           document.querySelector('#thumbnail').style.backgroundImage = '';
         });
 
     var videoElementInitializePromise;
     if (this.currentCast_) {
       videoPlayerElement.setAttribute('casting', true);
 
@@ skipping 337 matching lines @@
 var initPromise = Promise.all(
     [new Promise(initVideos.wrap(null)),
      new Promise(initStrings.wrap(null)),
      new Promise(util.addPageLoadHandler.wrap(null))]);
 
 initPromise.then(function(results) {
   var videos = results[0];
   player.prepare(videos);
   return new Promise(player.playFirstVideo.wrap(player));
 }.wrap(null));